WAKE FLOWS BEHIND 2-DIMENSIONAL MODEL HILLS

Laser-Doppler measurements of velocity characteristics are reported for the recirculating flow established in the wake of two-dimensional, polynomial-shaped obstacles that are axisymmetrical about a vertical axis and mounted in a water channel downstream of a fully developed channel flow for Re = 6 x 10(4). The study involves measurements of the mean and fluctuating flow properties in the streamwise and spanwise directions and includes comparison of the flow around a single obstacle with that resulting from the interaction of consecutive obstacles. The results include analysis of the turbulent stresses in local flow coordinates and reveal flow structure qualitatively similar to that found in other turbulent flows with a reattachment zone and, for the case of multiple hills, resembling the flow over wavy surfaces of large amplitude. The implications of the results for the calculation of turbulent flows over curved boundaries using turbulence models are discussed.